1. Field of the Invention
The present invention relates to a toner cartridge for use in a developing device and the developing device for an image forming apparatus for performing an image formation by an electrophotography process using toner that is supplied through a toner supply port from a toner cartridge by rotation of an agitator attached to a rotating shaft provided in the toner cartridge. In particular, the invention relates to a developing device for an image forming apparatus capable of preventing leakage of toner from a toner cartridge.
2. Description of Related Art
Heretofore, there have been proposed various types of developing devices for an image forming apparatus, e.g., a laser printer and the like. Many of the developing devices are constituted as a unit capable of being detachably mounted on a laser printer and also are provided with an exchangeable toner cartridge serving as a toner storing portion.
An embodied example of such the developing device is described referring to FIG. 17. FIG. 17 is an explanatory view of schematically showing a main part of the conventional developing device.
In FIG. 17, the developing device has a toner cartridge 100 which accommodates therein toner. The toner cartridge 100 is provided with a toner exhaust port 101 and an agitator 103 for agitating toner. In a frame F of a process unit supporting the toner cartridge 100, a toner introduction port F0 is formed corresponding to the toner exhaust port 101 of the toner cartridge 100. The frame F includes an upper frame F1 and a lower frame F2 which form a closed developing chamber 102. In the developing chamber 102, a toner supply roller 104 is rotatably disposed and a developing roller 105 is arranged adjacent to the supply roller 104. Thus, toner is supplied due to rotation of the agitator 103 from the atoner cartridge 100 through the toner exhaust port 101 and the toner introduction port F0 into the developing chamber 102. Rotation of the toner supply roller 104 then causes supply of the toner onto the developing roller 105.
A blade 107 is secured on an inner wall of the upper frame F1, above the developing roller 105, by a fixing member 106. This blade 107 serves to regulate the thickness of a toner layer formed on a circumferential outer surface of the developing roller 105. The developing roller 105 is disposed so as to be in contact with a photosensitive drum 108. An electrostatic latent image can be formed on a circumferential outer surface of the photosensitive drum 108 by a light exposure unit (not shown) which scans the surface of the drum 108 with laser light in accordance with image data. The developing roller 105 then performs toner development by supplying toner on the electrostatic latent image formed on the surface of the photosensitive drum 108. The developed image is transferred onto a paper sheet fed from a paper supply unit (not shown) to form the visual image thereon.
In the toner cartridge 100 of the conventional developing device, rotation of the agitator 103 in the toner cartridge 100 is caused by the driving power of motors disposed outside the toner cartridge 100. Therefore, a power transmitting member for causing rotation of the agitator is inserted in a port formed in the toner cartridge 100. A sponge member is firmly attached to the power transmitting member so as to be compressed toward the port by a pressing member of the power transmitting member, thereby closing the port.
When a rotation speed of the agitator 103 becomes higher, the sponge member tends to rotate along with the agitator owing to a large frictional power generated between the sponge member and the pressing member of the power transmitting member, which may cause leakage of toner through gaps between the sponge member and the port of the toner cartridge 100 to the outside. The leaked toner may stick to other portions in the image forming apparatus, for example, the outer surface of the toner cartridge 100, which may make operator's hands dirty in an exchanging operation of the toner cartridge 100. The leakage of toner is desired to be perfectly prevented from occurring.
To prevent the rotation of the sponge member, it is conceivable that, for example, a double-sided adhesive tape is provided on the sponge member whereby the sponge member is secured on the inner surface of the toner cartridge 100. At the time of assembling of the agitator 103 in the toner cartridge 100, however, a removing operation to remove releasable paper from the double-sided adhesive tape is troublesome and the adhesive surface of the tape may stick to unwanted portions except a predetermined portion in the toner cartridge 100, causing a long time for assembling them. Additionally, toner leakage may caused if the sponge member is adhered through the double-sided adhesive tape to a position displaced from a predetermined position in the toner cartridge 100.